Air filter medium



July 16, 1935. A. NUTTING 2,308,560

AIR FILTER MEDIUM Filed Dec.- 29, 1952 Fig. 1 24 Fig. 3

INVENTOR. Arthur" Nufiing mam ATTORNEY Patented July 16, 1935 UNITEDSTATES PATENT OFFICE AIR FILTER MEDIUM Application December 29, 1932,Serial No.649,241

5 Claims.

' This invention relates to air filter mediums and proposes certainnovel improvements in filter mediums 'of the flat, blanket or pad typeand particularly those fabricated by winding long strands of wire aroundspaced sup-' ports progressively from one end of the supports to theother. With filters of this type means are usually provided for holdingthe strands in their original positions so as to preserve'the uniformdistribution of the strands and thereby prevent their separation and theconsequent impairment of the filtering density provided by the pad as awhole.

The principal object of this invention is to provide a construction ofthis character in which the strands are arranged in a manner such thatthey cooperate to hold each other and thereby eliminate the necessity ofspecial holding means.

Another object is to provide a pad of this general type which can be socheaply manufactured as to render its replacement after a normal periodof use economically feasible.

The invention is illustrated in the accompanying drawing wherein:

Figure l is a front elevation of a pad which is partly broken in orderto bring out more clearly the relation of the various elements making upthe pad;

Figure 2 is a section along line 22 of Figure l; and

Figure 3 is a front elevation of an alternative construction.

In carrying out my invention I utilize a strand of material having ahard, roughened or jagged surface, the sharp protuberances or iags ofwhich are rigid. Steel wool is a particularly suitable material, notonly because of its surface roughness and low cost, but also because itcan now be obtained in standard rolls, a form which facilitates thefabrication of the filter medium into a blanket or pad. Any suitablemethod of winding or otherwise arranging the strands to form the pad canbe utilized. In a construction of the character shown in Figures 1 and2, this is usually done by winding the strands of steel wool aroundopposite sides of a supporting frame -I progressively from one end ofthe frame to the other. This results in the formation of separate layers2 extending acrosswopposed faces of the frame I. The filtering densityprovided by these layers can be controlled or regulated during thewinding by controlling the spacing of adjacent strands where one strandthickness is" desired, or, by building up the thickness of the layerswhere more than one strand thickness is wanted. Naturally thedistribution of the strands will be made uniform in order'to provide auniform filtering density.

Now in accordance with my invention another set of layers 3 aresimilarly wound over the frame I in a manner such that the strands ofthese layers extend at an angle to the strands of the layers 2 withwhich they contact. With a rectangular frame as shown, this is mosteasily accomplished by winding the layers 3 over the other two opposedsides of the frame I so that the strands of the layers 3 extend at rightangles to, and in engagement with, the strands of the layers 2. Withthis arrangement I have discovered that the strands of the separatelayers, by virtue of their rigid jags, interlock so effectively andfirmly as to hold'each other in their original or wound positions andthereby firmly preserve or maintain the uniformity of the filteringdensity provided by them. In other words the strands of one layermutually cooperate by surface contact with the cross strands of theother layers to prevent the separation which might otherwise occur as aresult of the handling and vibration to which they are subjected duringmanufacture, shipment and use. It may be noted that the interlockingeffect of the strands is so pronounced that it is unnecessary to providemeans for holding the free ends of the strands. Furthermore, theinterlocking effect is. substantial enough to permit the cleaning of thepads, either by vibration where a dry pad is utilized, or, by soaking inoil where a pad of the viscous impingement type is used.

In Figure 3 apad of this general type which is less expensive tomanufacture, is shown. In this construction the arrangement of thelayers 2 and 3 is the same as that of Figures 1 and 2 but the use of asupportingframe eliminated. In the construction shown in Figures 1 and 2the sup- 40 porting frame maintains the pad in a flat condition. Inorder to maintain the pad of Figure 3 ina fiat condition it is welded atintervals as indicated at 4, the welded portions extending at an angleto the strands of the outside layer. These welded portions furthermoreare made short and widely separated dn order to prevent curling orwaving of the marginal edges of the strands, a condition which wouldresult from a continuous line weld. Such condition is undesirablebecause it prevents the accurate fitting of the pad as a whole into theoutside filter frame ordinarily provided. This latterconstruction isparticularly intended for insertion into a frame composed of a material,such as card-board, so

that the entire filter can be disposed of by buming after a normalperiod of use. In this connection it may be noted that the strands ofsteel wool ordinarily used for filtering purposes are so thin that theywill readily burn when fire is applied.

Having described my invention I claim:

1. A filter pad having at least two mutually engaging layers of strandedmetallic material arranged so that the strands of one layer extend at anangle to the strands of the other layer, the strands of both layerspresenting a jagged surface having rigid jags by virtue of which thecrossed strands interlock with each other at the points of contact.

2. A filter pad having asupporting frame, a layer of stranded metallicmaterial having a jagged surface wound over said frame with the strandsextending in parallel relation, the jags of said surface being rigid,and another layer of similar material similarly wound over said framewith its strands extending at an angle to and in surface interlockingcontact with the strands ofthe first layer.

3. A filter pad having a rectangular supporting frame, a layer ofstranded material having a jagged surface wound over two opposed sidesof said frame progressively from one end to the other with the strandsextending in parallel relation, the Jags of said surface being rigid,and another layer of similar material similarly wound over said framewith its strands extending at right angles to and in surfaceinterlocking contact with the strands of the first layer.

4. A filter pad having at least two mutually engaging layers of materialin the form of wire strands arranged so that the strands of one layerextend at an angle to the strands of the other layer, the strands ofboth layers presenting a jagged surface having rigid jags by virtue ofwhich the cross strands interlock with each other at the points ofcontact, and means for holding said layers in a fiat condition, saidmeans consisting .of a series of short welds substantially spaced fromeach other.

5. A filter pad having an inner layer of stranded metallic material, andan outer layer of similar material wound over said inner layer, thestrands of one layer extending at an angle to the strands of the otherlayer and the strands of both layers presenting a jagged surface havingrigid lags by virtue of which the crossed strands interlock with eachother at the point of contact.

ARTHUR NU'ITING.

